Neither your nor my interpretation of an online purchase is a correct one. An online purchase from a computer in one country at a web server in another can be treated as both an import (by a purchaser) and an export (by a seller). But since a sale is typically solicited by a purchaser (it's driven by those who purchase), I'd say it's an import rather than an export.

> liquor to be shipped to the US and the liquor store would be expected to comply with US import rules

It may want to comply with the rules, because the parcel will bounce at customs, but if there are no export restrictions, it has no other reason not to send a bottle into the US.